KINETIC STUDIES OF YEAST NUCLEOSIDE DIPHOSPHATE KINASE

Initial velocity, product inhibition, and isotopic exchange studies have been carried out on crystalline nucleoside diphosphate kinase from yeast, with the magnesium complexes of adenine and uridinenucleotides as reactants. The kinetic mechanism is Ping-Pong (the first product dissociates before the second substrate combines with the enzyme), and all reactants give competitive substrate inhibition by combining with the improper stable enzyme form. A stable phosphoenzyme was isolated which may contain a phosphohistidine linkage. All of the kinetic constants have been determined and shown to be consistent with the Haldane relationships. An analysis of the kinetic constants suggests thatthe turnover numbers are the maximum possible for the physiological conditions. © 1969, American Chemical Society. All rights reserved.